1. Field of the Invention
The present invention relates to vehicular safety devices, and more particularly, to a seat belt system comprising a lap belt that can be used independently of an associated shoulder belt.
2. Background of the Invention
FIG. 1 shows a prior art seat belt system that is designed to protect a person, passenger or a driver, who is seated on seat 10 of a vehicle. The system comprises webbing 102, sliding latch plate 140 and buckle 150. First end 112 of webbing 102 is secured to the vehicle at an area at about the level of the person""s shoulder. Second end 114 of webbing 102 is secured to the vehicle at an area at about the level of the person""s hip. A seat belt pretensioner (not shown) can be installed at either first end 112 or second end 114 to provide tension on webbing 102. Inertia reels can also be placed at any vehicle mount to provide tension. In addition, pretensioners (including buckle pretensioners which can provide tensioning in both the lap and shoulder webbing) can be equipped with the seat belt system.
As shown in FIG. 1, first end 112 and second end 114 are secured to the vehicle on one side of the person while buckle 150 is secured to the vehicle on the opposite side. Sliding latch plate 140 comprises slot 142 and tongue 144. Webbing 102 is fed through slot 142 such that sliding latch plate 140 can slide along the full length of webbing 102. Buckle 150 is secured to the vehicle at an area at about the level of the person""s hip, but on the opposite side of second end 114. When in use, tongue 144 of sliding latch plate 140 is engaged in buckle 150, thus allowing shoulder belt portion 110 of webbing 102 to rest over one shoulder of the person and across his or her body, and lap belt portion 130 of webbing 102 to rest over the lap of the person. When the vehicle experiences a sudden deceleration, the body of the person leans forward and causes a tensile force to exert on shoulder belt portion 110. Since slot 142 is free to slide along webbing 102, the tensile force is transferred to lap belt portion 130 as well.
While this seat belt system is common to ground vehicles such as automobiles, it is less desirable for airborne vehicles such as airplanes. In the aviation industry, particularly for airplanes having side facing seats, it is preferable to have a safety belt system comprises a lap belt that can be worn independently of an associated shoulder belt. Such a system allows a passenger to be secured by the lap belt, without being restricted by the shoulder belt during normal level flight.
FIG. 2 shows another prior art system that is used in the aviation industry today. System 200 comprises shoulder belt webbing 210, shoulder belt latch plate 220, lap belt webbing 230, lap belt latch plate 240, and buckle 250. Manual lap belt and shoulder belt adjusters are often used.
First end 212 of shoulder belt webbing 210 is secured to the vehicle. A shoulder belt pretensioner (not shown) can be provided to exert tension on shoulder belt webbing 210. Second end 214 of shoulder belt webbing 210 is attached to shoulder belt latch plate 220. Shoulder belt latch plate 220 comprises snap slot 222. The safety belt system can be equipped with supplemental safety device 216. An example of supplemental safety device 216 is the Inflatable Tubular Torso Restraint (ITTR) manufactured by Simula Technology, Inc. of Phoenix, Ariz. The ITTR is fully disclosed in U.S. Pat. No. 5,839,753 (issued to Yaniv et al.), which is hereby incorporated by reference in its entirety.
First end 232 of lap belt webbing 230 is attached to lap belt latch plate 240, while second end 234 of lap belt webbing 230 is secured to the vehicle, on the same side of seat 20 where shoulder belt webbing 210 is secured. Lap belt latch plate 240 comprises snap stud 242, slot 246, and tongue 244. Snap stud 242 is adapted to receive snap slot 222. Tongue 244 is adapted to fit into buckle 250. Buckle 250 is secured to the vehicle.
A tensile force can be exerted on shoulder belt webbing 210 in one of several ways. For example, if seat 20 is in a forward-facing orientation, when the vehicle experiences a sudden deceleration, the body of the passenger leans forward and causes a tensile force to be exerted on shoulder belt webbing 210. In addition, the tensile force can be exerted when supplemental safety device 216 is deployed. Unlike in the system of FIG. 1, however, the tensile force exerted on shoulder belt webbing 210 in this system is not transferred to lap belt webbing 230. There is no transfer of tensile force in this system because shoulder belt webbing 210 and lap belt webbing 230 are independent of each other. In other words, since lap belt webbing 230 is permanently attached to lap belt latch plate 240, and lap belt latch plate 240 is attached to buckle 250 that is secured to the vehicle, the tension in shoulder belt webbing 210 cannot be transferred to lap belt webbing 230. This allows the passenger""s lower torso to move, thereby increasing the possibility of occupant injury during crashes. As a result, lap belt webbing 230 does not receive any benefit from supplemental safety device 216 or the shoulder belt pretensioner.
The present invention is a seat belt system that allows transfer of tension from a transferor belt, e.g., the shoulder belt, to a transferee belt, e.g., the lap belt. A preferred embodiment of the present invention can be used with a supplemental safety device such as the ITTR referenced above.
A preferred embodiment of the present invention comprises a shoulder belt webbing (the transferor belt), a shoulder belt latch plate (the transferor plate), a lap belt webbing (the transferee belt), a lap belt latch plate (the transferee plate), a buckle, and a tension transfer latch plate. During normal use, the lap belt latch plate and the tension transfer latch plate act as one unitary component. When the shoulder belt webbing is pulled and/or the supplemental safety device is deployed by a tensile force that is greater than or equal to a design predetermined value, the tension transfer latch plate separates from the lap belt latch plate and pulls the lap belt webbing. This invention allows the tension transfer latch plate to act as a fixed latch plate until the shoulder belt webbing receives a sufficient tensile force to pull the tension transfer latch plate such that it separates from the lap belt latch plate and tightens the lap belt webbing. It is noted that in another embodiment the shoulder belt webbing can be adapted to become the transferee belt and the lap belt webbing can be adapted to serve as the transferor belt.
A preferred embodiment of a tension transfer latch plate assembly of the present invention comprises a transferee plate and a tension transfer latch plate. Each of the plates preferably has, for example, an injection molded plastic cover or other device to prevent webbing tears and to keep the plates together during normal everyday use. The tension transfer latch plate assembly can also guide, position, and retain the tension transfer latch plate via detents in both the injection molded plastic covers. The transferee belt can be routed so that the tension transfer latch plate pulls from the assembly at a predetermined load when the transferor belt is pulled and/or when the supplemental safety device is deployed.
FIGS. 3, 3a, and 3b are schematic diagrams of a preferred embodiment of the present invention in which a shoulder belt is the transferor belt. Lap belt webbing 330 loops through lap belt latch plate assembly 340 and tension transfer latch plate assembly 360. Tension transfer latch plate assembly 360 is attached to lap belt latch plate assembly 340. Lap belt latch plate assembly 340 has tongue 344 that is adapted to engage with buckle 350. Shoulder belt latch plate 320 is adapted to engage with tension transfer latch plate assembly 360 by one of several known quick-release mechanisms. Preferably, the quick-release mechanism comprises snap slot 322 (the female member) and snap stud 362 (the male member). The slot or the stud may be part of shoulder belt latch plate 320 or the transfer latch plate assembly 360, respectively (as shown) or vice-versa.
When shoulder belt webbing 310 attached to shoulder belt latch plate 320 experiences a tensile force that is equal to or greater than the design value, the tensile force pulls shoulder belt latch plate 320. Since shoulder belt latch plate 320 is engaged to tension transfer latch plate assembly 360 via the quick release mechanism, the tensile force is transferred from shoulder belt latch plate 320 to the tension transfer latch plate assembly 360. Since tension transfer latch plate assembly 360 is attached to lap belt webbing 330 via slot 447 in lap belt latch plate assembly 340, as tension transfer latch plate assembly 360 moves away from lap belt latch plate assembly 340, it pulls lap belt webbing 330 through slot 447 in lap belt latch plate assembly 340. Since lap belt latch plate assembly 360 is anchored to buckle 350, tension is developed in lap belt webbing 330 and the occupant is held firmly in the seat.